IME: make WindowInsetsController.show(ime()) more robust

We need to make sure the served view is up-to-date, otherwise we might
erroneously reject or allow a request to show the IME via WindowInsetsController.

Fixes: 190217891
Bug: 200051968
Test: atest WindowInsetsControllerTests#\
        testShowIme_immediatelyAfterDetachAndReattach
Merged-In: Ib41412d5d5636bdc236aa94c4ee4702686b6d10f
Change-Id: Ib41412d5d5636bdc236aa94c4ee4702686b6d10f
(cherry picked from commit e6b4e24b30)

core/java/android/view/inputmethod/InputMethodManager.java

@@ -2154,6 +2154,7 @@ public final class InputMethodManager {
      * @hide
      */
     public boolean requestImeShow(IBinder windowToken) {
+        checkFocus();
         synchronized (mH) {
             final View servedView = getServedViewLocked();
             if (servedView == null || servedView.getWindowToken() != windowToken) {